Abstract
The clearance between the stationary volute and rotating impeller of a centrifugal pump is crucial; however, it affects the internal flow and deteriorates the pump performance. This study performed a flow investigation through a numerical simulation to understand the effect of clearance and pumping fluid viscosity under the design and off-design conditions of a centrifugal pump. Numerical simulations were conducted by solving unsteady Reynolds-averaged Navier-Stokes (URANS) equations and validated using experimental results. Five three-dimensional centrifugal pump flow domains were created, by varying the clearance thickness, and simulated with three different fluid properties. Consequently, the numerical simulation results aided in understanding the internal flow pattern and estimating energy loss due to disk friction and leakage through the clearance. It was found that the disk friction and leakage losses, which cause secondary losses in the pump, were highly affected by the fluid properties and clearance thickness. The clearance thickness drastically affected both the volumetric and hydraulic efficiencies to leakage; however, beyond a particular value, it became less significant. Furthermore, the viscous oils caused a high disk friction loss; however, the leakage loss was less affected by the clearance thickness.
•The pump performance was significantly affected by the thickness of the clearance at the shroud side, and radial leakage into the inlet side.•The increase in the pumping fluid viscosity increased the disk friction loss; however, the loss owing to leakage was reduced.•The pump efficiencies significantly decreased when Cl increased from 0 to 0.25 mm; however, beyond Csh = 0.50 mm, the drop became insignificant.•The volumetric efficiency loss for low viscous fluid was high, whereas the hydraulic efficiency loss was higher for highly viscous fluids.